Better Laser for Optical Communication Developed

The backbone of the Internet is comprised in large part by lasers and optical fiber, as optical communication can transmit prodigious amounts of data rapidly and efficiently. As the world demands greater bandwidth though, the technology is approaching its limits. Researchers at the California Institute of Technology however, have developed a new laser which could potentially increase optical data transmission rates by orders of magnitudes.

For forty years, distributed-feedback semiconductor (S-DFB) lasers have been used to send the optical signals along the cables. The reason it was first used and continued to be used is its spectral purity. The light it produced was very near a single frequency, and the more pure the light is, the faster digital bits can be transmitted. Unfortunately part of the laser's design limited its spectral purity, and while it was satisfactory in the past, it may not be in the future. The problem was that the III-V semiconductors used to produce the light also absorbed some of it, which degrades the spectral purity. The Caltech researchers have found that this absorption can be prevented by adding a layer of silicon to act as a concentrator. The silicon will pull the light away from the III-V semiconductor, but will not absorb the light itself.

This new laser could reduce the spread of frequencies to be 20 times narrower than that of the S-DFB lasers in use today. Such an improvement could greatly help the Internet keep pace with our demands for higher speed.